1. Field of the Invention
The invention relates to multimedia multipoint servers (MMS). More particularly, the invention relates to methods and apparatus for setting-up and re-establishing multimedia circuit connections between an MMS and remote sites through ATM, ISDN, or other types of networks.
2. State of the Art
Multimedia communication involves the exchange of audio, video, and data between two or more multimedia devices (typically PCs with attached video cameras) at different locations. When there are only two PCs involved, the connection between the PCs is relatively simple, provided that the two PCs use the same multimedia standard (for example H.320) and that a connection of sufficient bandwidth is available. However, when multiple PCs are involved, relatively complicated connections are often required. The complexity of the connection of multiple PCs is exacerbated by the fact that there are several different standards for multimedia communication, e.g. Motion JPEG, MPEG-2, H.320, etc. Each of these standards specifies a different encoding scheme and has its own bandwidth requirements. It is often desirable to interconnect several PCs, each of which is equipped for a different multimedia standard. In addition, these multimedia standards can be transported over data connections of different bandwidth capacities (e.g., ISDN, ATM, etc.). This also complicates the interconnection of multiple PCs for multimedia conferencing.
The issues involved in multimedia "multipoint" conferencing (multimedia conferencing among multiple PCs) have been addressed in the art and a partial solution has been provided through the use of a multipoint control unit (MCU). One such MCU is the General DataComm Multimedia Multipoint Server (MMS). The MMS is a switching device which includes support for the several different multimedia standards and the ability to convert from one standard to another. PCs may be directly connected to an MMS or may be connected to an MMS via a public or private telecommunications network. The MMS may be coupled to different types of telecommunications services such as an ISDN gateway server and an ATM switch. Typically, an MMS unit and its interconnection to remote PCs is managed by a network manager (a human being) who programs the MMS and arranges for the circuit connections to remote PCs. A multimedia conference must be reserved in advance by contacting the network manager who then determines whether the necessary MMS resources are available to conduct the conference at a particular time. Alternatively, a reservation system of the type described in previously incorporated co-owned applications may be used. If a reservation system is used, the network manager is relieved of the task of determining the availability of necessary resources and booking the conference. After a conference has been reserved, the telecommunications connections (e.g. ATM and ISDN connections) to remote PCs must be set-up by the network manager shortly before the conference begins or as permanent connections. The setting up of ISDN connections may be partially automated, but the setting up of ATM connections must be performed manually by the network manager. Due to the complexity of setting up these connections, they are typically set up once as permanent connections which wastes network bandwidth.
As mentioned above, the MMS may be connected to an ISDN gateway server, an ATM switch, or some other telecommunications equipment. The network manager associated with the MMS typically communicates with the server(s) and the switch(es) via a complex signalling protocol using software provided by different equipment vendors. While there are standard signalling protocols for ATM switches and ISDN servers, different switch and server manufacturers implement the protocols in different ways with their own proprietary software. The server(s) and the switch(es) respond to commands from the network manager to set up connections between the MMS and the remote PCs. When setting up the connections between the MMS and the remote PCs, the network manager must be cognizant of the bandwidth requirements for each remote PC and the multimedia standard in place at each of the remote PCs. Some standards require separate communications channels for audio and video, whereas other standards use a single channel for audio and video. In the case of ATM connections, the virtual circuit set-up from the MMS to a remote PC may involve several ATM switches and several connections. If a conference participant who is not connected to the MMS via a permanent connection leaves the conference and later wishes to return to the conference, a new connection will need to be established for that participant.
From the foregoing, it will be appreciated that as multimedia multipoint conferencing becomes more popular, it will require a more automatic operation than the state of the art systems provide. Although reservation systems have partially automated the operation of multimedia conferences, it would be desirable if the connection set-up could also be automated. However, the complex user network interfaces (UNIs) and signalling protocols used to set up connections make the automation of circuit set-up very difficult. Moreover, the common practice of providing "permanent" ATM connections wastes bandwidth and it would be preferable to provide ATM connections only as needed.